The present invention relates to an intake arrangement for an internal combustion engine, and more specifically to an intake arrangement for a multi-cylinder internal combustion engine having a plurality of engine cylinders.
In the multi-cylinder internal combustion engine, as lengths of intake air passages extending to the engine cylinders become more equalized to one another, undesirable dispersion or change in intake volumetric efficiency between engine cylinders is more reduced. This can improve engine output and suppress vibrations of the engine. In addition, waveform, namely, wave amplitude and phase, of induction noise caused by intake air that is introduced into the engine cylinders via the intake air passages, can be rendered uniform by the equalized intake air passages to thereby produce clear engine sound. Thus, it is desirable to equalize the lengths of the intake air passages in an intake arrangement for the internal combustion engine.
Japanese Patent Application First Publication No. 2000-161163 discloses an intake manifold including a surge tank, an intake pipe connected to one side wall of the surge tank, and branch pipes connected to an opposite side wall of the surge tank. The branch pipes are independently coupled to the corresponding engine cylinders. A distance from the connection of the surge tank and the intake pipe, to the connection of the surge tank and each of the branch pipes is substantially the same. Specifically, the connection of the intake pipe with the surge tank is located at a generally middle position in the longitudinal direction of the surge tank. The connection of the outside branch pipes disposed on the opposite sides in the longitudinal direction of the surge tank, with the surge tank is offset from the connection of the inside branch pipes disposed between the outside ones, with the surge tank, in a lateral direction perpendicular to the longitudinal direction of the surge tank.
Japanese Patent Application First Publication No. 8-334069 discloses an intake arrangement including an intake collector, a throttle chamber connected to one longitudinal end portion of the intake collector, and a plurality of branch pipes each having one end coupled to a side wall of the intake collector and the other end coupled to the corresponding engine cylinder.